Atlantic Council: The United States and its allies must be ready to deter a two-front war and nuclear attacks in East Asia

Introduction

“If hostilities were to renew on the [Korean Peninsula] it is not a matter of ‘if’ the Chinese Communist Party will intervene, it is when … This has been a very difficult topic for us to address as an alliance.”— Retired Gen. Robert Abrams, former commander of US Forces Korea (USFK)¹

“I’ve wargamed conflicts with China and with North Korea dozens of times. If we look at a map and consider the forces involved, it is almost impossible for either to occur without some form of simultaneity.”—US defense official, name withheld

“If the political survival of Xi Jinping or Kim Jong Un is at stake in [a] military conflict they are losing, escalating to a limited nuclear strike would be rational … hesitating to use nuclear weapons would be the irrational act.”—US intelligence official, name withheld

The challenges to deterrence in East Asia have begun to change fundamentally in recent years, putting them on track to present grave risks to US national security interests over the coming decade. This report summarizes the results of a study focused on two of these emerging and interrelated challenges to deterrence in East Asia. The first is the potential for a conflict with either the People’s Republic of China (PRC) or North Korea to escalate horizontally and become a simultaneous conflict with both. The other is the possibility that either or both adversaries would choose to escalate vertically to a limited nuclear attack—rather than concede defeat—in a major conflict.

US thinking about war in East Asia often neglects the possibility that the United States would have to fight the PRC and North Korea simultaneously rather than separately. Furthermore, conventional wisdom in the United States underestimates the risk that either the PRC or North Korea would resort to a limited nuclear strike in the event of a conflict in the region. However, the recent behavior of the United States’ adversaries in East Asia suggests that this thinking may be off the mark; the PRC military has reorganized itself to prepare to fight a two-front war, while both the PRC and North Korea continue to develop the sophistication and size of their tactical nuclear arsenals.

To better understand the threats posed by these two major risks five to ten years from now (in the 2027-2032 timeframe), we conducted a series of workshops and interviews with key government personnel and experts, and analyzed our findings in this report, originally written for the US Defense Threat Reduction Agency (but not necessarily representing its views). These findings should serve as a wake-up call: The United States and its allies can no longer think about conflicts with the PRC and North Korea in isolation from each other, and they must take urgent action to prepare for the possibility of facing limited nuclear attacks in an East Asia conflict scenario.

Key findings

If a conflict with one adversary in East Asia doesn’t end quickly, expect it to widen. If a conflict is initiated by either the PRC or North Korea, the potential for expansion to simultaneous conflicts with both would pose a high risk to US and allied defense objectives, particularly because this would impose severe operational and strategic challenges. During this study, we found many plausible pathways from which a conflict with one could expand into conflicts with both, even without Beijing and Pyongyang coordinating with one another. Though it is ill-advised to confidently predict the flow of a conflict up to a decade from now, such pathways are sufficiently numerous and plausible that—if a conflict with either the PRC or North Korea does not conclude quickly—we should anticipate that simultaneous conflicts with both could result.

• Deep distrust currently exists between the PRC and North Korea, and we found that neither is likely to feel compelled by any obligation to fight alongside the other—but this would not prevent the emergence of simultaneous conflicts with both. Advance coordination between the two is one of the less likely ways such simultaneous conflicts could emerge. We identified a series of far more plausible pathways, depicted in Figures 1 and 2.
• Simultaneous conflicts impose challenges so severe that the risk should still be considered high, even if the probability of these two conflicts occurring simultaneously is uncertain. The logistical challenges alone are daunting, given the requirements of such major conflicts, including stocks of precision standoff munitions and missile-defense interceptors. Operationally, simultaneous conflicts would force overstretched US command-and-control (C2) systems to make hard choices about how to allocate limited numbers of their most valuable assets. Meanwhile, alliance management and escalation management would become exponentially more complex.
• If North Korean aggression triggers a successful counteroffensive by the US and South Korea, this will likely prompt the PRC to intervene to protect its interests as North Korea collapses. Such intervention would likely spark a confrontation in the context of US-PRC rivalry and distrust, which could escalate to military conflict. Further, Beijing would likely be willing to risk a conflict to prevent Seoul and Washington from dictating the terms of Korean unification via an unchecked counteroffensive.
• Any major US-PRC conflict—for example, if the PRC attacks Taiwan—is likely to escalate horizontally and engulf Korea, unless the US-PRC conflict is a limited war with a quick, decisive outcome. In such a conflict, Beijing is likely to strike US regional bases, possibly including US Forces Korea (USFK) bases well within mutual striking distance of the PRC mainland. Even if the South Korean military and USFK are initially fenced off from hostilities, either side could view them as a US tool to break a stalemate or be drawn in as the PRC attacks US bases in Japan by overflying Korea. Additionally, Beijing could encourage Pyongyang to escalate in order to tie down US and ROK forces. Whether or not Beijing does, a US-PRC conflict would disturb North Korea’s escalation calculus. US reinforcements flowing to the region, along with US commitments and losses, could prompt opportunistic or preemptive aggression from North Korea—particularly because the conflict’s outcome would have immense implications for Pyongyang.
• A second conflict need not even escalate very far for such challenges to come into play. As a major conflict with the PRC or North Korea begins, the potential for escalation to draw in the other immediately affects the political and military options available to the United States and its allies, even if war is averted. Seoul’s efforts to avoid being dragged into a US-PRC war, for example, could constrain US forces in South Korea. Meanwhile, US and South Korean efforts to avoid a war with the PRC could hamstring US-South Korean operations in the Yellow Sea, or in mountainous areas near the PRC-North Korean border.

The risk that a war in East Asia would go nuclear is rising, as the PRC and North Korea have increasing incentive and capabilities for limited nuclear attacks. The risk of a limited nuclear attack by the PRC or North Korea in the event of conflict is likely to grow through the 2027–2032 time frame, and simultaneous conflicts would exacerbate this risk. Building on the results of another study we conducted but have not made public, “Preventing Strategic Deterrence Failure on the Korean Peninsula,” this study found that North Korea has been rapidly advancing its capability and intent to initiate a limited nuclear attack in the event of conflict.³ Though the study did not find evidence as compelling to show that the PRC is currently moving aggressively in this direction, it found evidence that the PRC’s capability to employ nuclear weapons for operational and tactical purposes is increasing.

• North Korean weapons capabilities and policy have moved rapidly toward enabling limited nuclear attacks. Pyongyang’s September 8, 2022, nuclear policy declaration set the stage and justification for limited nuclear attacks, stating that nuclear first use is an option to retake the initiative in a conflict, for example.⁴ Meanwhile, since January 2021, North Korea has been sounding a drumbeat on its tactical nuclear capabilities, including tests of claimed tactical nuclear-capable missiles and displays of a new tactical nuclear warhead.